Various manual and powered tools for installing and removing tires from wheel rims are known. In a manual version such tools generally comprise an elongated pry bar handle, which is gripped by a user, and a flattened tool end for insertion between the tire bead and the wheel rim. The bead of a tire is generally wire reinforced and resists deformation. The bead is usually intended to seal a mounted tire to the wheel rim. For this purpose the bead has a diameter that is somewhat less than the diameter of the wheel rim flange and resides between the spaced flanges of the wheel rim. The bead resists stretching is urged axially against the rim and sealed to the rim, inter alia, by pneumatic pressure in the tire or in an inner tube in the tire.
To remove a tire from a rim, the beads are unsealed or "broken" by moving them axially inwardly to disengage from sealing engagement with the rim. Then the two beads and sidewalls of the tire are passed axially over one of the rim flanges to remove the tire from the rim. Inasmuch as the diameter of the bead is less than that of the rim, this involves forcing the bead over the rim, by stretching the bead and/or deforming the bead into an oval and moving the longer dimension of the oval around the rim.
A working end of a tool is inserted between the tire bead and the rim flange. The user applies pressure to the opposite handle end, using the tool as a lever and the wheel rim as a fulcrum. A short length of the tire bead is lifted axially over the rim flange. This process is repeated in successive stages to increase the length of the bead on the axial outside of the rim flange, often using two or three pry tools around the periphery of the wheel rim to hold a portion of the bead against popping back over the rim flange while more of the bead is pried over the rim flange. After a certain angular span has been passed over the rim flange, prying at a distance from that span (e.g., at a diametrically opposite position) pulls the bead portion that is already outside the rim radially inwardly on the outside, rather than tending to pull that portion back between the rim flanges. It becomes easier to pass the remainder of the bead axially over the rim until the entire tire bead resides outside the rim.
Powered machines are available to serve the same function. The wheel is mounted on a spindle and the bead is broken. A short length of the tire bead is pried over the rim flange. A tool is placed under the lifted bead and engaged with a driving shaft on the spindle, whereupon an end of the tool is passed circumferentially around the periphery of the wheel rim flange, pulling the bead over the rim flange.
To fully remove the tire, the opposite side bead is passed over the same rim flange as the first bead, in a similar manner. For installing a tire on a wheel rim, the foregoing process is carried out in reverse order, manually or using powered means.
The wheel rim has a diameter greater than the diameter of the bead of the tire, for sealing. Additionally, axially inwardly from the rim, the diameter of the wheel is substantially less than the diameter at the flanges. Similarly, the internal diameter of the tire is greater at the tread than at the beads. As a result, the wheel rim flanges permit lateral displacement of a tire on the wheel rim (i.e., radial displacement whereby the tire is rendered eccentric relative to the wheel axis). Moving the bead radially inwardly between the wheel flanges (or outside of them) permits that bead on the opposite side of the wheel to be moved radially outwardly and passed axially over the outside diameter of the rim. This facilitates tire installation and removal.
For example, to remove a conventional automobile tire from a wheel rim, the tire is deflated. The seals between the tire beads and the rim flanges are broken. In this unpressurized state, the tire beads no longer abut against the wheel rim flanges, and can be pressed axially inwardly from the rim flanges, as well as displaced radially in the reduced diameter area axially between the rims. A pry bar is inserted between the tire and the wheel rim and is used to pry a portion of the tire bead axially over the wheel flange (rim), thus drawing a short length of bead over the wheel rim to a position axially outside of the rim. The tire can be shifted laterally relative to the center of the tire rim to provide clearance in the direction of prying while temporarily pulling the bead on the diametrically opposite side of the wheel radially inwardly. This process is continued around the periphery of wheel rim, temporarily shifting the tire laterally (radially) in the direction of prying until the tire bead has been passed over the wheel rim all around the rim circumference.
After the bead of a pneumatic tire is broken, the tire sidewalls are readily displaceable or simply buckle axially inwardly from lack of pressure pushing the sidewalls outwardly and engaging the bead against the rim. However, tires that are more rigid, such as heavy duty tires, tractor tires, low profile automobile tires and so called "run-flat" tires mechanically retain their sidewall shape and the position of the tire bead against the inner surface of the rim flange, even after the tire is deflated (if applicable) and/or after the seal between the tire bead and rim flange has been broken. It can be significantly more difficult to pry the bead of a rigid tire over the rim than for a flexible light duty pneumatic tire.
Conventional powered tire processing machines, e.g., for removal of pneumatic automobile tires, require the user initially to pry a portion of the tire bead over the wheel rim to engage the machine tooling. For rigid tires this task can be virtually impossible for a single person to accomplish. It may require separating the tire bead from the rim flange on one side of the wheel while simultaneously inserting a pry bar between the tire bead and the rim flange on the opposite side of the wheel and prying a portion of the tire bead over the rim. Perhaps recognizing that existing machines are deficient in this regard, equipment manufactures have recently introduced machines which are intended for removal and installation of rigid tires. For example, the Only Coats Model No. 9010E manufactured by Henessey Industries, Inc. of LaVergne Tenn. comprises a series of pneumatically operated swing-in mounted rollers for flexing and holding the sidewalls of rigid tires. These new generation machines may be effective, but they also are expensive.
What is needed is an effective but less-expensive way to remove and install tires, especially relatively rigid tires that require more than a momentary bead-breaking pressure to disengage the tire from the rim. Advantageously, the same tool should assist a manual operation or an automated and machine-powered operation, and should be usable in a wide variety of different operations.